1. Field of the Invention
The present invention relates to a recording apparatus, and more particularly to an apparatus capable of recording video data having different frame rates.
2. Related Background Art
A digital camera has been known conventionally which records video signals on a memory card or the like. The digital camera of this type often uses a CCD sensor or a MOS sensor as an image capture element. The CMOS sensor has advantages over the CCD sensor in that a consumption current is smaller and a data read speed is higher. By utilizing these advantages, it becomes possible nowadays to capture moving image signals at a high frame rate by driving a CMOS sensor at high speed.
Japanese Patent Application Laid-Open No. H07-298112 (corresponding foreign application: U.S. Pat. No. 5,640,202) describes a moving image capture system capable of making variable a frame rate of an image capture apparatus constituted of an image capture element, A/D conversion means, a signal processing unit and image signal compressing unit.
A digital camera writes captured moving image data on a recording medium in accordance with an audio video interleaved (AVI) scheme. A frame rate of moving image data is generally faster than a data write rate of a recording medium. Therefore, moving image data rate is lowered by utilizing various image compression technologies, and a write timing of a recording medium is adjusted by using a buffer memory.
There are needs of a long time image capture and a high speed frame rate.
As the moving image data frame rate (the number of frames per unit time) becomes high, the moving image data rate becomes high. Since a buffer may overflow, a single image capture time is limited by the capacity of a buffer.
If the moving image frame rate is low and if it is lower than an allowable data write rate of a recording medium, the single image capture time is limited by the capacity of a recording medium.
It is therefore difficult to satisfy both a long time image capture and a high speed frame rate.
A scene with a high speed object such as a sports event is desired in some cases to capture moving images at a high speed frame rate.
However, a presently available recording format of moving image data cannot change a moving image data frame rate intermediately during image capture.
Even if moving image data is recorded by changing a moving image data frame rate intermediately during image capture, the moving image data is reproduced at one of frame rates.
Therefore, a low speed frame rate section is reproduced at a normal speed, whereas a high speed frame rate section is reproduced at a slow motion speed.
Changing a frame rate during image capture has been impossible essentially because the images cannot be reproduced as desired.